In industrial sewing, it has long been known that precision of the feeding and control of the fabric through the sewing area is of primary concern, particularly in the area of upholstery fabrics and mattress covers. Due to the thickness of these fabrics, the amount of lift of the presser foot above the throat plate is also a concern.
Various efforts have been made to improve the control and feed of the fabric such as providing a feed belt to work in combination with the feed dog or feed belt in lieu of the feed dog as is illustrated in U.S. Pat. Nos. 1,661,023; 2,241,230; 5,383,418 to Turner et al; Wilmoth; and Block et al. To date, no arrangement has been presented which satisfactorily meets the necessary fabric feed and control requirements.
The instant invention has for its primary object a fabric feed system for a sewing machine which positively grips and controls the fabric as it is moved through the sewing area.
Another object of the invention is a feed system for a sewing machine which utilizes an upper feed belt in cooperation with a lower feed belt to grip and move the fabric through the sewing area.
Another object of the invention is a presser foot which guides the upper belt through the sewing area and positions it in engagement with the fabric during sewing.
Another object of the invention is a presser foot which presents a multi-level pressure surface.
Another object of the invention is a mounting assembly for the lower feed belt which is positionable in an operative position and a cleaning position.
Another object of the invention is a lower belt feed system which includes a plurality of feed belts.
Another object of the invention is a drive system which drives the upper and lower feed belts in synchronism with each other and with the movement of the sewing needle.
The instant invention is directed to a sewing machine assembly which comprises a machine frame, a machine drive, a sewing area which includes a presser foot and at least one reciprocating sewing needle, and a cloth plate having a work surface over which a fabric work piece travels to and through the sewing area. A continuous lower feed belt is positioned to rotate over the feed plate, beneath the presser foot and through the sewing area. A lower belt drive, which is driven by a feed drive, is connected with the machine drive, is adapted to drive the lower belt in rotary step movement in synchronism with the reciprocating movement of the sewing needle. A lower belt housing, which carries the feed plat, the lower belt drive and the lower belt, is positionable between an operative position in which the lower belt and the cloth plate are positioned beneath the presser foot in the sewing area and an inspection position in which the lower belt and the cloth plate are separated from the presser foot and the sewing are. The feed drive is operative to drive the lower belt drive with the belt housing in the sewing position or the inspection position.
The assembly also includes a continuous upper feed belt positioned to rotate over the feed plate, over the lower belt and beneath the presser foot. The presser foot is mounted with a presser bar which is adapted to move the presser foot between a raised position in which the upper feed belt and presser foot are separated from the lower feed belt and an operating position in which the presser foot positions the upper feed belt in engagement with the lower feed belt in the sewing are. The upper belt is also driven by the feed drive and an upper belt drive. The upper belt assembly includes a drive gear, idler pulleys, a tensioning device and the presser foot. The tensioning device, which includes a pneumatic cylinder and an idler roller, acts to maintain the upper belt under proper tension with the presser foot in the raised position and in the lowered position.
If desired there may be two lower belts arranged in spaced side by side positions over the cloth plate. Also, if desired, a second upper belt may be provided to cooperate with the second lower belt.
The presser foot includes a groove defined by inner and outer presser ramps, each ramp has a lower fabric contact surface. The fabric contact surfaces of each ramp are disposed along vertically spaced horizontal planes. A material feeding system for cooperative use with at least one reciprocating sewing needle wherein sewing is accomplished. The feeding system includes a sewing area including a presser foot, a cloth plate having a work surface over which a fabric is advance, at least one continuous lower feed belt formed with a gripping surface comprising a plurality of spaced teeth arranged to move over the work surface and through said sewing area, and at least one continuous upper feed belt formed with a gripping surface comprising a plurality of spaced teeth arranged to move over at least a lower belt, through the sewing are and beneath the presser foot. A presser bar mounts the presser foot and acts to position the presser foot and the upper belt in a raised position in which material may be positioned in the sewing area and a lowered position in which the presser foot and the upper belt are moved toward the lower belt and into engagement with the material being sewn.
Upper and lower drives move the upper and lower belts in step rotational motion about belt mountings in synchronism with the reciprocating motion of the sewing needle.
The arrangement allows the fabric to be inserted into the sewing area with the presser foot in the raised position where it is first gripped and then drawn beneath the presser foot through and out of said sewing are by the upper and lower feed belts with said presser foot in the lowered position. The presser bar is driven by a piston between upper and lower positions to move the presser foot between the raised and lowered positions. The piston acts to raise and lower the presser foot a distance of about one inch.
The drive of the sewing needles and of the loopers is substantially conventional and is substantially disclosed in various prior disclosures such as U.S. Pat. Nos. 2,241,230 and 5,664,510.